Targeting adjustment

ABSTRACT

A targeting system for aligning an axis of a targeting sleeve and a bore in a distal end portion of an intramedullary nail is proposed, the targeting device comprising a distal targeting arm with a first end being configured to be coupled to a trailing end of an intramedullary nail, an adjusting device, the adjusting device being configured to be coupled to the distal targeting arm. The adjusting device may comprise an adjusting element and a nail follower including two targeting holes each being configured to receive a sleeve assembly. The adjusting element may cooperate with the nail follower such that the positions of the two targeting holes are adjustable so as to correspond to respective locking holes at a leading end of the intramedullary nail, even when the nail is bent.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present is a continuation of International Application No.PCT/EP2013/061831 filed Jun. 7, 2013, the disclosure of which is herebyincorporated herein by reference.

FIELD OF THE INVENTION

The invention relates to a distal targeting device, in particular to adevice for adjusting an axis of a sleeve for inserting a locking screwrelative to a bore axis in a distal end portion of an intramedullarynail. Furthermore, the invention relates to a method for operating thedevice.

BACKGROUND OF THE INVENTION

An intramedullary nail may be implanted in a fractured bone, such as atibia or a femur, the implantation being such that the nail extendsdistally and proximally with respect to the fracture, in reinforcementof fractured parts of the bone that have been re-aligned or merely areto be held in alignment for the course of healing repair.

Intramedullary nails of the character indicated are usually preparedwith two spaced parallel holes that extend diametrically across the nailnear the distal end of the nail and may be prepared with two spacedholes of similar nature, but not necessarily parallel, near the proximalend of the nail. These holes are formed to accept bone screws, and whenthe nail has been installed, its bone-screw holes are said to be “blind”in terms of the bone-drilling alignment that must be achieved.

The problem has always been one of assuring correct alignment fordrilling a hole to accept a bone screw driven through bone for anchoringpassage through the intramedullary nail. One of the problems of locatinga bone-screw hole in an installed intramedullary nail is the practicalfact that the nail may have undergone a slight bend in the course ofimplantation, so that such holes at the distal end of the nail no-longerhave precisely the same location with respect to the proximal end, aswas the case prior to nail implantation.

EP 2 049 025 A1 describes a targeting device for targeting a cross borein a bone nail, the targeting device comprising an arm member coupled toan end portion of the bone nail and an aiming portion forming part ofthe arm member extending parallel to a longitudinal axis of the bonenail. An adjustable aiming device is mounted on the aiming portion, theadjustable device having a guide bore alignable with the cross bore inthe nail. The adjustable device is moveable with respect to the aimingportion in a direction perpendicular to a plane containing both the naillongitudinal axis and central axis of the cross bore. A target indicatoris mounted on the adjustable aiming device. Here, the adjustment isperformed based on an x-ray image generated when the nail is alreadyinserted into the bone.

BRIEF SUMMARY OF THE INVENTION

An object may be to provide an improved device and a method fortargeting a screw hole in a distal end portion of an intramedullarynail, i.e. aligning an axis of a targeting sleeve with an axis of thescrew hole, in particular allowing a compensation of a bending of thenail.

This is achieved by the subject-matter of the respective independentclaims. Further embodiments are described in the dependent claims.

In general, a targeting system for aligning an axis of a targetingsleeve and a bore in a distal end portion of an intramedullary nailcomprises a distal targeting arm with a first end being configured to becoupled to a proximal end, i.e. a trailing end of an intramedullarynail, an adjusting device, the adjusting device being configured to becoupled to the distal targeting arm. The adjusting device may comprisean adjusting element and a nail follower including two targeting holeseach being configured to receive a sleeve assembly. The adjustingelement may cooperate with the nail follower such that the positions ofthe two targeting holes are adjustable so as to correspond to respectivelocking holes at a distal end, i.e. a leading end of the intramedullarynail, even when the nail is bent.

According to an embodiment, the adjusting element of the targetingdevice may comprise at least one screw having a thread which engageswith a threaded hole in the nail follower.

Assuming that the targeting holes are in positions which align with thelocking holes in the nail, i.e. the nail follower is in a neutralposition, when the distal targeting arm is coupled to the proximal endof the not yet inserted intramedullary nail, and further assuming thatthe nail is slightly bent in response to forces applied by the bone ontothe already inserted nail, the adjusting element is configured to forcethe nail follower from the neutral position to a position whichcorresponds to the position of the nail portion of the bent nailincluding the locking holes.

It will be understood that also other mechanical means, for example acam mechanism with a lever, may be provided to achieve the intendedfunction of adjusting of the position of the nail follower.

In one embodiment, the adjusting element of the targeting devicecomprises two screws wherein a first screw includes a first thread witha first pitch and a second screw includes a second thread with a secondpitch, wherein the first pitch differs from the second pitch and whereinthe first and second screws are coupled by a gear system of at least twointermeshing gears with a gear ratio of 1:1, i.e. the first and secondscrews may simultaneously rotate by the same circumferential angle whenthe adjusting element is operated.

According to a further embodiment, the adjusting element of thetargeting device comprises two screws with equal pitches, wherein thetwo screws are coupled by a gear system with a gear ratio different from1:1, i.e. the two screws may simultaneously rotate by differentcircumferential angles relative to each other, when the adjustingelement is operated.

Otherwise, the nail follower may be configured to be deformed so as toadjust the position of the targeting holes. Such deformation may becaused by at least one screw as described in the previous embodiments.

According to an embodiment, a first end portion of the nail follower maybe coupled to the targeting arm by a first pivot axis and a second endportion of the nail follower may be coupled to the targeting arm by asecond pivot axis, and the nail follower may be configured to bedeformed so as to adjust the position of the targeting holes by means ofan adjusting device being arranged between the two pivot axes. Due tothe pivot axes, it may be possible to achieve a continuous bending ofthe nail follower along its length, i.e. without an inversion of thebending direction.

It is noted that it is intended to displace the first one of the twotargeting holes by a length which is different to the length by whichthe second one of the targeting holes is displaced. It will beunderstood that each of the above mentioned concepts alone as well asany combination thereof is suitable to achieve this.

According to an embodiment, the position of a first one of the targetingholes is displaced by a first length and the position of the second oneof the targeting holes is displaced by a second length, when theadjusting element is operated, wherein the first length may be 5 to 15percent larger than the second length, in particular 8 to 12 percentlarger than the second length, and for example 10 percent larger thanthe second length.

According to an embodiment, the adjusting element may comprise twoscrews, wherein a first one of the two screws may rotate in an oppositedirection relative to a second one of the two screws, when the adjustingdevice is operated.

According to an embodiment, a first threaded bore in the nail followermay be arranged adjacent of a first one of the two targeting holes and asecond threaded bore in the nail follower may be arranged adjacent of asecond one of the two targeting holes, with the axes of the threadedbores being oriented transverse to the axes of the targeting holes.

According to an embodiment, the nail follower may comprise a firstmember including a first one of the targeting holes and a second memberincluding a second one of the targeting holes, wherein the first memberand the second member may be movable relative to each other so as toadjust the position of the targeting holes.

According to a further embodiment, the adjusting device of the targetingdevice may further comprise a housing including a plurality ofradio-opaque markers with a distribution allowing a determination of a3D-orientation of the housing based on a 2D x-ray image.

According to another aspect, a method of operating the targeting deviceas described above may comprise the steps of receiving an x-ray imagegenerated in a plane defined by at least one of the axes of thetargeting holes and a main axis of an intramedullary nail to which thetargeting device is coupled, determining a deviation of the axis of thetargeting hole and an axis of a related one of two screw holes in theintramedullary nail based on the received x-ray image, and operating theadjusting element of the adjusting device so as to align the axis of thetargeting hole with the axis of the related screw hole, thereby alsoaligning the axis of the other one of the targeting holes with therespectively related one of the two screw holes in the intramedullarynail.

According to another embodiment, the method may further comprise thestep of adjusting an x-ray imaging device like a C-arm based X-rayimaging device so as to generate an x-ray image in the plane defined bythe axis of the targeting sleeve and the main axis of the intramedullarynail. The x-ray imaging device may further be adjusted so as to generatean x-ray image with an angle relative to the intramedullary nail of 50to 70 degree, for example of 60 degrees.

According to a further embodiment, the method does not include any stepof inserting an intramedullary nail into a bone, leading to a situationin which an intramedullary nail is positioned in a bone, in so far asthe step constitutes a treatment of a human or animal body by surgery.

It has to be noted that embodiments of the invention are described withreference to different subject-matters. In particular, some embodimentsare described with reference to method-type claims, whereas otherembodiments are described with reference to apparatus-type claims.However, a person skilled in the art will gather from the above and thefollowing description that, unless otherwise notified, in addition toany combination of features belonging to one type of subject-matter,also any combination of features relating to different subject-mattersis considered to be disclosed with this application.

These and other objects, features and advantages of the exemplaryembodiments of the present invention will become apparent upon readingthe following detailed description of exemplary embodiments, when takenin conjunction with the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be detailed by way of exemplary embodiments withreference to the attached drawings.

FIG. 1 is an isometric visualization of a targeting system for anintramedullary nail.

FIG. 2 shows an isometric view of an adjusting device according to afirst embodiment.

FIG. 3 a is a side view of an adjusting device according to the firstembodiment.

FIG. 3 b is a sectional view of the adjusting device of FIG. 3 a.

FIG. 4 is a detail view of a mid-portion of an adjusting deviceaccording to a second embodiment.

FIG. 5 is an illustration of an adjusting device according to a thirdembodiment.

FIG. 6 is an illustration of an adjusting device according to a fourthembodiment.

FIG. 7 is an isometric view of an adjusting device according to a fifthembodiment.

FIG. 8 is an isometric view of an adjusting device according to a sixthembodiment.

FIGS. 9 a to 9 c are schematic illustrations of x-ray images generatedduring a method.

FIG. 10 is a flowchart representing method steps.

It is noted that the illustration in the drawings is only schematicallyand not to scale.

Throughout the drawings, the same reference numerals and characters,unless otherwise stated, are used to denote like features, elements,components, or portions of the illustrated embodiments. Moreover, whilethe present invention will now be described in detail with reference tothe figures, it is done so in connection with the illustrativeembodiments and is not limited by the particular embodiments illustratedin the figures, as defined by the appended claims.

DETAILED DESCRIPTION

FIG. 1 provides an isometric illustration of an embodiment of atargeting system for an intramedullary nail, the system comprising anadjusting device 100 and a targeting arm 200. An intramedullary nail 400is coupled at a proximal end thereof with a first end 210 of thetargeting arm. The targeting arm 200 further comprises holes 220 asreceipts for the adjusting device 100. The targeting arm may comprise aplurality of holes 220 so that the adjusting device may be coupled tothe targeting arm at different positions so as to adapt the position ofthe targeting holes of the adjusting device to the positions of thelocking holes in the distal end portion of different intramedullarynails with different lengths.

Further shown in FIG. 1 is a sleeve assembly 300 which extends throughone of the targeting holes in the adjusting device 100. Here, the axisof the sleeve assembly 300 is aligned with the axis of a first lockinghole 420 in the nail 400. The sleeve assembly may comprise an outertissue protection sleeve, a drill sleeve as well as a trocar.

FIG. 2 is an isometric illustration of an adjusting device 100A. Theadjusting device 100A generally comprises an adjusting element 110A, anail follower 120A and a housing 130A. These elements will be describedin detail based on different embodiments in conjunction with thefollowing figures.

FIGS. 3 a and 3 b show an embodiment of an adjusting device 100A, withFIG. 3 a being a plane view of the front side and FIG. 3 b being asectional view of the back side of the adjusting device 100A. In thisembodiment, the adjusting element 110A comprises a knob 112A, a firstscrew 114A, a second screw 116A as well as a mechanical gear 118A. Theknob 112A is arranged at the top of the housing of the adjusting device100A and is coupled with the first screw 114A so that the first screwcan be rotated by operating the knob. The rotational movement of thefirst screw 114A is transmitted by means of the gear system 118A fromthe first screw to the second screw 116A so that the screws are coupledso as to rotate simultaneously. According to the embodiment, the firstscrew 114A may have a right-hand thread and the second screw 116A mayhave a left-hand thread. The gear system 118A may have two intermeshinggears or tooth wheels engaging each other.

The first and second screws engage with respective threaded holes in thenail follower 120A. According to the embodiment, the pitch of the firstthread may be larger than the pitch of the second thread. With theright-hand thread rotating in an opposite direction as the left-handthread, and with the two different pitches, it can be achieved that thenail follower will be moved so that the first targeting hole 122A isdisplaced by a greater length as the second targeting hole 124A.

The nail follower 120A comprises a nail follower body 126A and two nailfollower members 128A. The nail follower body includes slightly curvedouter edges which may engage in a groove 132A formed in the housing 130Aof the adjusting device. The curved outer edges allow a movement of thenail follower body so that the nail follower body is canted or angledwith respect to the parallel screw axis by the action of the two screws.The two nail follower members 128A are provided in the nail followerbody 126A, wherein the nail follower members comprise straight contactsurfaces, respectively, so that the nail follower members may slidealong each other due to an action of the two screws. The threaded boresfor accommodating the screws 114A, 116A are provided in the nailfollower members 128A, respectively.

The aspect, that the first targeting hole is displaced differentlyrelative to the second targeting hole is further illustrated in FIG. 4which is a detailed view of the mid-section of the adjusting device 100Bparticularly showing the engagement of the first screw 114B and thesecond screw 116B with the nail follower 120B. For illustrativepurposes, and arc section denoted with A is drawn in to show the path ofthe first targeting hole 122B, when the nail follower 120B is moved. Onthe other hand, a substantially straight line denoted with B is drawn into show the path of the second targeting hole 124B.

It is noted that FIG. 4 shows an embodiment in which the first andsecond screws 114B, 116B both include the same threads, i.e. bothinclude right-hand or left-hand threads. These screws may be coupled bya gear which transmits a rotation from the first screw 114B to thesecond screw 116B such that the screws rotate in the same direction andsimultaneously. This might be achieved by means of a tooth belt or by asequence of tooth wheels. To achieve the different displacement of thetargeting holes, as shown in FIG. 4, the pitches of the two screws maydiffer from each other or alternatively a gear ratio different from 1:1may be realized by the gear between the two screws.

FIG. 5 shows another embodiment of an adjusting device 100C mounted on adistal targeting arm 200C, the adjusting device having a nail follower120C which is formed as a bendable or deflectable beam. By means of onescrew as an adjusting element it is possible to deform the bendablebeam, i.e. the nail follower 120C so as to have a curved distal endportion. Such bending is indicated by the dotted lines denoting the axisof the nail follower 120C in the respective condition. Consequently, thefirst targeting hole is displaced by a greater length than the secondtargeting hole.

A further embodiment is shown in FIG. 6, including a further adjustingdevice 100E. Having both adjusting devices 100D and 100E being mountedon the targeting arm 200D, but at different positions relative to thenail follower 120D, which is also in this embodiment formed as abendable beam, a complex bending of the nail follower may be possible.The adjusting element of the further adjusting device 100E may engage ina screw-nut (not shown) which may be provided in or at the nail follower120D, with the screw-nut being pivotable relative to the nail followerso as to allow a continuous bending of the nail follower along itslength and past the adjusting element of the adjusting device 100E.

This embodiment may take into account that an intramedullary nail maycome in contact at different locations of the medullary channel with theinner bone tissue and forces may apply accordingly on different sectionsof the nail. As shown in FIG. 6, the mid-portion of the nail follower120D may be pressed downwardly whereas the distal end portion is pulledupwardly, as indicated by the two arrows in FIG. 6.

It will be understood that even more than two adjusting devices may beprovided along the nail follower.

FIG. 7 illustrates yet another embodiment of the targeting devicecomprising an adjusting device 100F with a nail follower 120F formed asan elongated beam. A first end of the nail follower may be coupled to orintegrally formed with a proximal portion of the targeting arm 200F,whereas the second end of the nail follower may be adjustably coupled toa distal portion of the targeting arm. Here, the adjusting device 100Fcomprises an attachment element 140F with a lever allowing aquick-fastening of the adjusting device at the distal portion of thetargeting arm. It will be understood that a slight pivot movement of thehousing 130F relative to the attachment element 140F should be allowedas the distal portion of the nail follower 120F will tilt as soon as thebendable beam will be bent. The adjusting device according to thisembodiment comprises only one screw 114F with a knob 112F as anadjusting element.

Exemplarily, the housing 130F is provided with fiducial markers formedas radio-opaque balls 150F. A plurality of such radio-opaque markerswith a specific distribution allows a determination of a 3D-orientationof the housing based on a 2D x-ray image. Consequently, a determinationof a viewing angle or a position of one element relative to anotherelement, for example as described in conjunction with FIGS. 9 a to 9 c,may be performed based on a single x-ray image.

FIG. 8 illustrates another embodiment including a bendable nail follower120G, allowing to adjust the positions of sleeve assemblies 300G so asto be aligned with locking holes in an intramedullary nail 400G. Here,the nail follower is coupled to the distal targeting arm 200G at bothend portions of the nail follower. Further, the adjusting device 100G isarranged in a middle section between the two end portions.

Operating the adjusting element 110G may push or pull the middle sectionof the nail follower and thus bend the same.

The nail follower 120G may be coupled to the targeting arm by means ofpins each providing a pivot axis. This may allow a continuous bending ofthe nail follower beyond the pivot axes, when the adjusting element 110Gis operated.

FIGS. 9 a to 9 c show a series of sketches schematically illustrating asequence of stages during a process of adjusting a screw axis relativeto a bore axis. It is noted that for reasons of clear view the targetingsystem and in particular the adjusting device is omitted in the sketchesof these figures.

In the stage of FIG. 9 a, a first x-ray image has been generated showingthe distal end portion of the intramedullary nail 400H inside a bone500H, i.e. a femur. Also visible is a sleeve assembly 300H. In thisimage, the axis 410H of the intramedullary nail 400H is inclinedrelative to the axis 310H of the sleeve assembly 300H. Based on oneimage like that of FIG. 9 a, or based on more than one image ifnecessary, a position and orientation of an imaging device may bedetermined. Particularly, the position and orientation of an imagingdevice relative to the imaged structures may be determined based on asingle x-ray image when this image includes a visualization of areference body formed by a plurality of radio-opaque markers with aspecific distribution.

Knowing the position and orientation of the imaging device allows for anadjustment of the imaging device to generate an x-ray image within theplane defined by the axis of the intramedullary nail and the axis of thesleeve assembly.

In the stage of FIG. 9 b, an image has been generated within the planedefined by the two axes 310H and 410H. As a result, these axes extendparallel to each other, as shown in the figure. The intramedullary nail400H is illustrated with a distal end portion being slightly bentdownwardly. Consequently, the axis 410H of the nail 400H is consideredas a main axis which is nevertheless straight so that the first lockinghole 420H and the second locking hole 430H are not anymore located onthis axis. On the other hand, this straight axis may define a planetogether with the axis of the sleeve assembly.

In the stage of FIG. 9 c, the position of the sleeve assembly 300H hasbeen adjusted so that the axis 310H of the sleeve assembly is alignedwith the axis of the first locking hole in the nail.

The flow-chart in FIG. 10 illustrates the principles of using oroperating the targeting device. It will be understood that the describedsteps are major steps, wherein these major steps might be differentiatedor divided into several sub-steps. Furthermore, there might be alsosub-steps between these major steps.

The schematically illustrated methods start at the circle denoted with‘start’.

In step S1, a first end of the targeting arm is coupled with anintramedullary nail which is already inserted into a medullary channelof a bone.

In step S2, the adjusting device is coupled to the distal portion of thetargeting arm. The position at the targeting arm depends on theconfiguration of the intramedullary nail, i.e. depends on the positionof the locking holes in the distal end portion of the intramedullarynail.

In step S3, a first x-ray image is generated with an imaging directionbeing inclined both relative to the nail axis as well as to the axis ofanyone of the targeting holes.

In step S4, the imaging direction is adjusted so that this directionlies within a plane defined by the nail axis and at least one of thetargeting hole axes. Furthermore, the imaging direction is adjusted soas to be between 20 and 40 degrees, in particular 30 degrees inclinedrelative to the targeting hole axes, i.e. so as to be between 50 and 70degrees, in particular 60 degrees inclined relative to the nail axis.

In step S5, a second x-ray image is generated allowing a determinationof a deviation of the distal portion of the intramedullary nail, inparticular of a first and a second locking hole from an expectedposition due to a bending of this portion of the nail.

In step S6, the adjusting element of the adjusting device is operated soas to displace the targeting holes correspondingly, i.e. according tothe determined deviation.

In step S7, the correct alignment of the axis of the targeting hole andthus of a sleeve assembly which can be received in the targeting hole,relative to the axis of the related locking hole in the intramedullarynail may be confirmed based on a further x-ray image.

The methods end at the circle denoted with ‘end’. Subsequently, a distallocking screw may be inserted through the locking hole to anchor thebone segment to the bone nail.

While the invention has been illustrated and described in detail in thedrawings and foregoing description, such illustration and descriptionare to be considered illustrative or exemplary and not restrictive. Theinvention is not limited to the disclosed embodiments. Other variationsto the disclosed embodiments can be understood and effected by thoseskilled in the art in practicing the claimed invention, from a study ofthe drawings, the disclosure, and the appended claims.

In the claims, the word “comprising” does not exclude other elements,and the indefinite article “a” or “an” does not exclude a plurality.

The mere fact that the certain measures are recited in mutuallydifferent dependent claims does not indicate that a combination of thesemeasures cannot be used to advantage. Any reference signs in the claimsshould not be construed as limiting the scope.

1. (canceled)
 2. A targeting system for a bore in a distal end portionof an intramedullary nail, comprising: a distal targeting arm with afirst end being configured to be coupled to a trailing end of anintramedullary nail; an adjusting device, the adjusting device beingconfigured to be coupled to the distal targeting arm, wherein theadjusting device comprises an adjusting element and a nail followerincluding first and second targeting holes each being configured toreceive a sleeve assembly; wherein the adjusting element includes firstand second screws which engage first and second threaded bores in thenail follower, the first and second screws can be rotated such that thepositions of the first and second targeting holes are adjustable so asto correspond to respective locking holes at a leading end of theintramedullary nail, when the nail is bent; and wherein the adjustingelement first screw includes a first thread with a first pitch and thesecond screw includes a second thread with a second pitch, wherein thefirst pitch differs from the second pitch and wherein the first andsecond screws are coupled by a gear with a gear ratio of 1:1.
 3. Thetargeting device of claim 2, wherein the adjusting element first screwrotates in an opposite direction relative to the second screw, when theadjusting element is operated.
 4. The targeting device of claim 2,wherein the first threaded bore in the nail follower is arrangedadjacent the first targeting hole in the nail follower and the secondthreaded bore in the nail follower is arranged adjacent the secondtargeting hole, with the axes of the first and second threaded boresbeing oriented transverse to the axes of the first and second targetingholes.
 5. The targeting device of claim 4, wherein the nail followercomprises first and second independent members, the first memberincluding the first threaded bore and targeting hole and the secondmember including the second threaded bore and targeting hole, whereinthe first member and the second member are movable relative to eachother by rotation of the first and second screw so as to adjust theposition of the targeting holes.
 6. The targeting device of claim 2,wherein rotation of the first and second screws in the first and secondthreaded bores of the nail follower respectively causes the position ofa first targeting hole to be displaced by a first length and theposition of the second targeting hole to be displaced by a secondlength, when the adjusting element is operated, wherein the first lengthis 8 to 12 percent larger than the second length.
 7. The targetingdevice of claim 2, wherein the adjusting device further comprises ahousing including a plurality of radio-opaque markers with adistribution allowing to determine a 3D-orientation of the housing basedon a 2D x-ray image.
 8. A targeting system for a bore in a distal endportion of an intramedullary nail, comprising: a distal targeting armwith a first end being configured to be coupled to a trailing end of anintramedullary nail; an adjusting device, the adjusting device beingconfigured to be coupled to the distal targeting arm, wherein theadjusting device comprises an adjusting element and a nail followerincluding first and second targeting holes each being configured toreceive a sleeve assembly; wherein the adjusting element includes firstand second screws which engage first and second threaded bores in thenail follower, the first and second screws can be rotated such that thepositions of the first and second targeting holes are adjustable so asto correspond to respective locking holes at a leading end of theintramedullary nail, when the nail is bent; and wherein the adjustingelement first screw and second screw have equal pitches, wherein thefirst and second screws are coupled by a gear with a gear ratiodifferent from 1:1.
 9. The targeting device of claim 8, wherein theadjusting element first screw rotates in an opposite direction relativeto the second screw, when the adjusting element is operated.
 10. Thetargeting device of claim 8, wherein the first threaded bore in the nailfollower is arranged adjacent the first targeting hole in the nailfollower and the second threaded bore in the nail follower is arrangedadjacent the second targeting hole, with the axes of the first andsecond threaded bores being oriented transverse to the axes of the firstand second targeting holes.
 11. The targeting device of claim 8, whereinthe nail follower comprises first and second independent members, thefirst member including the first threaded bore and targeting hole andthe second member including the second threaded bore and targeting hole,wherein the first member and the second member are movable relative toeach other by rotation of the first and second screw so as to adjust theposition of the targeting holes.
 12. The targeting device of claim 8,wherein rotation of the first and second screws in the first and secondthreaded bores of the nail follower respectively causes the position ofa first targeting hole to be displaced by a first length and theposition of the second targeting hole to be displaced by a secondlength, when the adjusting element is operated, wherein the first lengthis 8 to 12 percent larger than the second length.
 13. The targetingdevice of claim 8, wherein the adjusting device further comprises ahousing including a plurality of radio-opaque markers with adistribution allowing to determine a 3D-orientation of the housing basedon a 2D x-ray image.